Not Applicable
The present invention relates to devices and methods for removing a sample of tissue from a human or animal. In particular, the present invention pertains to devices and methods for conducting a biopsy to remove a sample or specimen of a tumor or lesion for examination and analysis.
In diagnosing and treating certain medical conditions, such as potentially cancerous tumors, it may be desirable to extract from a portion of suspicious tissue, such as a tumor, a specimen of the suspicious tissue for detailed examination and analysis. The process of removing such a specimen of tissue is referred to as a biopsy.
In many instances, the suspicious tissue to be examined is inside the patient""s body. For example, the suspicious tissue may be a tumor inside a human breast. To minimize surgical intrusion into the body, it is desirable to be able to insert a small instrument into the body for extracting a portion of the suspicious tissue.
Different types of instruments and procedures have been developed for conducting biopsies to extract a tissue specimen for analysis. One device that has been developed is the fine needle aspirator. This device comprises a hollow needle, the end of which is sharpened. The needle is inserted into the suspicious tissue so that individual cells or clusters of cells of the tissue lodge inside the hollow core of the needle. The needle is then extracted from the patient, and the cells and fluid removed from the needle for a cytological examination. In certain circumstances, however, it may be desirable to extract portions of tissue for a histological examination, a procedure that is not typically feasible using a fine needle aspirator.
Another type of tissue-sampling device for biopsies is exemplified by the device described in U.S. Pat. No. Re. 34,056xe2x80x94Lindgren et al. This type of device includes a forward stylet, which includes at its distal end a sharpened cutting surface. The stylet may be, for example, a needle sized between 12 and 20 gauge. Behind the sharpened cutting end of the stylet, along the shaft thereof, is a groove. A hollow cannula surrounds the stylet, and has its distal end sharpened to form a fine cutting edge. A mechanism is provided to move the stylet and the cannula forward separately. For example, springs may be used for this purpose. Preferably, the stylet and the cannula are moved forward rapidly so that the sharpened ends thereof may efficiently cut the tissue. In operation, the operator of this type of device first causes the stylet to be pushed forward through the tumor or suspect tissue. After the distal end of the stylet has passed through the suspect tissue, a portion of the tissue surrounding the stylet partially fills the groove on the shaft of the stylet. The cannula is then pushed forward so that the sharpened distal end of the cannula cuts off the portion of the tissue that has filled the groove on the shaft of the stylet, and encloses that tissue. The entire device may then be removed from the patient""s body, and the tissue trapped in the cannula removed for examination and analysis.
U.S. Pat. No. 5,526,822xe2x80x94Burbank et al. discloses another type of biopsy device that includes the ability to apply a vacuum to the groove in the stylet. This vacuum assists in drawing tissue into the groove, ensuring that a more substantial portion of tissue is severed by the cutting cannula. Using such a system, it is in some cases possible to use a relatively large stylet (e.g., a 7 to 14 gauge needle) to obtain a relatively large tissue sample.
All of the above-described systems use knife edges to a cut the tissue. The cutting edge must remain extremely sharp, so that it cuts the tissue cleanly. Moreover, the stylet and the cannula cutter must be propelled forward rapidly to provide a clean cut through the tissue. Elaborate mechanisms are typically employed to provide the rapid forward movement. Because the knife edges move rapidly, however, there is limited time for tissue to fill the groove on the stylet. Therefore, the system sometimes obtains a smaller sample than would be ideal. In addition, variations in tissue density and anatomy may cause the stylet to deflect from its ideal position in relation to the tissue to be penetrated.
Electrosurgical techniques have been used in a variety of circumstances, including certain types of biopsies. In electrosurgery, high frequency electrical energy is applied through a primary electrode to tissue. The electrical energy flows through the tissue to a return electrode. The tissue adjacent to the primary electrode is ablated, to form an opening in the tissue. The return electrode in monopolar electrosurgery may be a large electrode placed on the exterior of the patient""s body at a point remote from the primary electrode. In bipolar electrosurgery, the return electrode may be a smaller electrode positioned somewhat near the primary electrode. An exemplary biopsy instrument using electrosurgical techniques is described in International Publication No. WO 98/08441.
The present invention, in one aspect, is a novel electrosurgical tissue sampling device, or biopsy device, including a novel electrosurgical stylet. In another aspect, the present invention is a method of using the novel biopsy device to obtain a tissue specimen.
The novel stylet of the present invention includes a shaft that has a proximal end and a distal end. At the distal end of the stylet shaft is a substantially hemispherical head. A stylet electrode extends distally from the stylet head. The stylet electrode may be activated with radio frequency (RF) electrical energy to ablate the tissue adjacent the stylet electrode. A cannula that cooperates with the stylet also has a proximal end and a distal end. An opening is formed at the distal end of the cannula. The distal end of the cannula may be selectively separated from the stylet, or may abut the stylet to close the opening at the distal end of the cannula. Also at the distal end of the cannula is another electrode that also may be activated with radio-frequency electrical energy to ablate the tissue adjacent the distal end of the cannula.
The system may be monopolar, in which the return electrical path is provided by a return electrode attached to the patient""s body remote from the device. Alternatively, the system may be bipolar, in which the return electrical path is provided by a return electrode on the device itself. The same return electrical path may be used for both the electrode on the stylet and the electrode on the cannula.
In accordance with the method of the present invention, the electrode on the head of the stylet is energized. With the stylet in a withdrawn position abutting against the distal end of the cannula, the stylet and the cannula are pushed through the skin and the underlying tissue, while applying an RF current, until the head of the stylet is adjacent a targeted tissue mass (e.g., a lesion or tumor). Next, the stylet is extended distally from the distal end of the cannula so that its head penetrates the targeted tissue mass, whereby the stylet head and the distal end of the cannula are on opposite sides of the tissue mass. The electrode at the distal end of the cannula is then energized, and the cannula is pushed through the tissue mass toward the stylet head, thereby cutting a xe2x80x9ccorexe2x80x9d through the tissue mass that is captured as a tissue specimen within the distal end of the cannula. The cannula and the stylet are then removed from the patient""s body. After the cannula and the stylet have been removed, they may be separated from one another, and the tissue specimen enclosed within the cannula may be removed and examined.